There's no point in me trying to state a case for this being the best Bond film; no one thinks that. It wasn't the first Bond film I saw, and it came out before I was born – so it's not the Bond film that hit when I was whatever is considered the "right age" for liking Bond. I don't even have a nice story of the first time I saw it; I can't remember when that was. What I can say for sure is You Only Live Twice is the Bond film I have seen most often and I have enjoyed the hell out it every single time.

Ignoring almost all of the source novel (a bitter tale of a broken Bond seeking revenge on Blofeld for killing his wife), You Only Live Twice was assembled from ideas thought up by the production team during a long location scout in Japan. Newly minted megastar Connery was making noises about leaving: they needed to make Bond bigger than the actor playing him, and to make the film an event. They had no choice but to go large. A list of events and scenes was given to Roald Dahl, who had never written a proper screenplay before, to knock together into a story.

Dahl gave them a sly pastiche of a Bond movie, full of straight-faced camp, moments of wicked humour and overblown events that must have looked unfilmable when presented on the page. Not to mention the silliness in having Bond trying to blend in with his Japanese surroundings (which ends up with him looking more like a slouching Burt Reynolds).

As a result of its piecemeal assembly, You Only Live Twice is wildly uneven in tone: we get intimate and very tense scenes such as the poison dripping down the yarn towards a sleeping Bond, then we get scenes so overblown and cartoonish such as the helicopter with a magnet that carries off a carload of hoods chasing 007. (After they are dumped in the sea, there is a fine a example of actual humour in Bond one-liners: "Just a drop in the ocean.") You Only Live Twice may have marked the end of Bond as a serious spy series, but it makes for a livelier, more unpredictable movie. It's a lot of fun and almost does itself an injury in trying to entertain.

Bond is deployed well: Connery is relaxed and at home, the whole thing is confident without being smug. Connery's Bond, for all his talk of room-temperature sake and oriental studies at Cambridge, never had a whole lot of finesse – only two films ago he was trying to defuse a sophisticated atomic device by repeatedly hitting it with a gold brick. But he's great at following up leads: he does some decent detecting and spying here. He's even better at getting himself closer to where the action is, even if he has no idea what he's going to do when he gets there. There are two perfect examples of this: the first where he assumes the identity of an assassin he has just killed and is taken back to enemy offices, the second where he's moments away from being shot into space when he's disguised as an astronaut. Connery's Bond is also impressive when interacting with fellow agents, opposite numbers and members of the armed forces; there's a mutual respect, for example, when he's working alongside "Tiger" Tanaka. And he's resourceful, using whatever is to hand: during the office fight with an opponent twice his size, Bond picks up a settee and beats the huge thug with it.

Fundamentally, You Only Live Twice is a big movie: it has scope and size that few films, even the Bonds that followed, have matched. Blofeld has a huge rocket base hidden inside a volcano, complete with helipad, monorail, Mini Mokes and an almost unlimited number of henchmen. It was a set so huge they could, and did, fly a helicopter inside it. It's impressive rather than ludicrous. Well, maybe a bit of both. Every department of film-making delivers. Cinematographer Freddie Young gave it the epic look he had given to David Lean's films, set designer Ken Adam excelled himself with the colossal volcano set, John Barry's score is one of his best – the haunting Capsule in Space that soundtracks the opening spacejacking (and the demise of poor astronaut Chris) is outstanding. The dreamy Nancy Sinatra song is one of Bond's finest, too.

The film is full of moments that are still routinely mocked (Blofeld has a pool of piranhas that he terminates employees with), but it also has moments of greatness (the helicopter shot of Bond fighting a dozen or so dockworkers as he runs across a warehouse roof). We finally get to see Blofeld, and Donald Pleasence makes for a very creepy looking villain – although most of his job seems to be holding on to a clearly traumatised Persian cat (which never worked in film again). It was the first time many in the audience had seen now commonplace martial arts, or heard of sumo wrestlers or ninjas. There may not be much logic at play, but it's a wild, exotic movie that has spectacle and ambition. It's my favourite Bond movie, so there.

Favourite line: Tanaka: "The one thing my honourable mother taught me long ago was never to get into a car with a strange girl. But you, I'm afraid, will get into anything ... with any girl."

Favourite gadget: Little Nellie, Ken Wallis's autogyro, something that looks like it was invented for a Bond movie even though it wasn't.